Several different major/minor loops memory organizations or architectures are described in U.S. Pat. Nos. 3,618,054; 3,838,407 and 3,999,172. Typically, both the major loop and the minor loop are established by an arrangement of chevron or C-bar permalloy type circuits on a film of a magnetic garnet material. The bubble domains or bubbles are moved around the loop by a magnetic field which rotates in the plane of the magnetic material. The major loop is generally elongated such as to allow a number of minor loops to be aligned along the side. The major loop may be closed as shown in U.S. Pat. No. 3,618,054. With a closed major loop, two-way transfer gates permit the transfer of bubbles from the minor loops to the major loop and from the major loop to the minor loops.
Major loops may also be of the open type disclosed in U.S. Pat. Nos. 3,838,407 and 3,999,172 as is shown in FIG. 1. With the open type of major loop, one-way transfer gates from the write channel 10 of the major loop transfer bubbles into one side 12 of the minor loops and another transfer gate permits bubbles to be transferred out of the other end 14 of the minor loops into the read channel 16 of the major loop. Data information stored in the minor loop is circulated until the desired block of data consisting of one bit from each loop reaches the transfer points. On command of a read transfer signal from the decision-making means or control center 18, the information is transferred to the reach channel of the major loop whereupon it is read by a detector 20. The detected information, or alternatively new information is used to control the generation of bubbles at generator 22 which are subsequently propagated along the write channel of the major loop to the write transfer switches. On command of a write transfer signal from control center 18, the information is transferred from the write channel 10 into the minor loops 12. This organization has the following disadvantages. Any arbitrarily referenced bit or byte cannot be positioned at the detector for future reading without using the off chip signal path or without losing information that preceeds the bit or byte. Upon reading a stream of information that ends on an arbitrary bit or byte, the information that follows must either be passed through the off chip signal path or lost. Another disadvantage is that the use of the off chip signal path prior to and after a stream of information degrades the performance, i.e. throughput, of a multimodule bubble store. A further disadvantage is that the information that is read from the chip, passed through the signal path and then returned to the chip is exposed to data loss when it is in the signal path.
Another open major loop type architecture was described by Bonyhard in 1978 at the Indian Wells 3M Annual Meeting and is shown in FIG. 2. This organization has a replicator/annihilator 24 with one path going to the detector 20. Another path 26 goes from the replicator 24 to the generator/merge point 22 that is in the write channel 10. In this organization, a merge point 28 connects the read channel 16 and the write channel 10. With the system shown in FIG. 2, one needs to make a decision before he reads the data whether the data is to be annihilated at the replicator or not. Hence, this has the disadvantages of lack of flexibility. One cannot read information from the bubble chip and then on the basis of this information make a decision to restore it unchanged, change it or replace it on the chip.
In addition, one cannot read information from the bubble chip and then on the basis of this information make a decision to change or leave unchanged the bits or bytes that immediately follow the information read.